This invention relates generally to incandescent illumination systems or fixtures and, more particularly, to incandescent lamps adapted for use in combination with a concave reflector in collecting a high proportion of the emitted light and projecting a high-intensity beam with a smooth and even beam pattern.
Incandescent lamps of this particular kind are useful in theater, television, architectural, and general purpose lighting fixtures that provide high-intensity beams of light. In such fixtures, it is desirable to collect as high a percentage of the emitted light as possible and to redirect that collected light as a high-intensity beam having a desired intensity distribution. The most popular lighting fixtures of this type use reflectors that have various size diameters up to 8 inches in diameter and have focal points located 25 to 30 millimeters from the base of said reflector. Lamp manufacturers use these dimensions to make lamps that can easily and interchangeably be used in these reflector systems and fixtures.
Incandescent lamps of this kind commonly are used in combination with ellipsoid or near-ellipsoidal reflectors. The lamps are positioned with their light-emitting filaments located at or near a general focal point close to the reflector, such that emitted light impinging on the reflector is redirected through a gate to a lens that then projects the high-intensity beam.
Alternatively, such lamps can be used in combination with parabolic or near-parabolic reflectors. The lamp is positioned with its filaments at or near the reflector's general focal point such that emitted light impinging on the reflector is redirected to form the projected beam without the need for a lens. However, a lens sometimes is used to alter the projected beam's divergence or spread or to integrate the beam and thereby provide a desired intensity distribution.
Incandescent lamps used in illumination systems of this kind typically have included a filament in the form of one continuous coiled coil having a longitudinal axis. This type of filament is easier to manufacture because it generally has only two main contacts and support points. The filament typically is oriented with its longitudinal axis parallel to the longitudinal axis of the lamp and reflector.
A few lamps with their filaments perpendicular to the longitudinal axis, such as the DYS ANSI code lamp and others, have been made but the coiled coils of the filament are spaced apart at a distance that has been varied and unspecified. Also the longitudinal length of these coiled coil filaments have always been longer than the height or diameter of said filament and none have a spherical overall shape. Additionally these lamps are not able to be used with the reflector systems and fixtures listed above due to the fact that they are made with different types of lamp bases and shorter lamp envelopes that place the filament in the wrong position to align with the focal point of said reflector systems and fixtures.
Other incandescent lamps used in illumination systems of this kind have included a plurality of linear, helically-wound coils arranged in one or more parallel rows and various other configurations that form a light-emitting source. These complicated structures have been made in an effort to have more points of the filament fall at, or be closer to, the absolute center of the filament providing a light source that is closer to a point source. These types of filaments are more difficult to manufacture because they have multiple support points and contacts to be made to complete the filament circuit.
It is known that there is a single point in a reflector that is the most efficient point to place the light source and that point is known as the focal point. In theory this point should be a point source or infinitely small point. These facts do not change no matter what the size or shape of said reflector. Cunningham U.S. Pat. No. 5,268,613, and McBride, Jr., et al. U.S. Pat. No. 6,034,473 disclosed the need to compact the light source in an effort to make it more point source and therefore more efficient.
Filament manufacturing problems and stray light radiation problems become more enhanced where higher voltages and, or, wattages are desired due to the fact that the overall filament length increases and therefore mounting arrangements for these longer filaments become more complex making it much more difficult to control the light that passes through the central angular region. This in turn requires the design of more complex reflector and lens configurations in order to effectively reflect this light into the main beam of the reflector thereby trying to increase the candle power of a lamp for a particular wattage and voltage.
The incandescent lamps described briefly above have proven to be generally satisfactory for use in combination with concave reflectors in providing high-intensity beams of light. However, it is known that some of the emitted light impinging on the reflector is redirected in an undesired manner. This happens because the light is not being emitted from a single point, but multiple parts of the filament that is arranged in coiled coils or the plurality of linear, helically-wound coils. Additionally it is known that the area between these parts of the filaments block and absorb light that is generated by the interior parts of the filament and create shadows or cause emitted light from that area to be lower in intensity, thus causing an uneven projected beam field with hot spots, shadows, and, or cloudy areas. Cunningham U.S. Pat. No. 5,268,613, also discloses the need to smooth the projected beam of light.
It should, therefore, be appreciated that there is a need for an improved incandescent lamp for use with a concave reflector. Additionally, an improved means to allow the lamp to be used in combination with a specific size or size range of concave reflectors to project a controlled high-intensity beam with a higher collection efficiency, a more even or smooth field of illumination, and easiest possible method of manufacture. The present invention fulfills this need.